Biot number signifies the ratio of

Consider a two-dimensional laminar flow over a long cylinder as shown in the figure below.

The free stream velocity is $${U_\infty }$$ and the free stream temperature $${T_\infty }$$ is lower than the cylinder surface temperature $${T_s}.$$ The local heat transfer coefficient is minimum at point

For laminar forced convection over a flat plate, if the free stream velocity increases by a factor of $$2,$$ the average heat transfer coefficient

A hemispherical furnace of $$1$$ $$m$$ radius has the inner surface (emissivity, $$\varepsilon = 1$$) of its roof maintained at $$800K,$$ while its floor $$\left( {\varepsilon = 0.5} \right)$$ is kept at $$600K$$. Stefan-Boltzmannn constant is $$\,5.668 \times {10^{ - 8}}$$ $$W/{m^2}.{K^4}.$$ The net radiative heat transfer (in $$kW$$) from the roof to the floor is __________.